This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-083332, filed Mar. 22, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a recording medium, signal recording method and apparatus and signal reproducing apparatus in which information is recorded and reproduced in a predetermined track form.
Recording tracks on recording media are formed with physical addresses in units of a predetermined recording capacity. The physical addresses take the form of embossed pits or other marks. The recording/reproducing method and apparatus have the recording error preventing capability. The same applies to recording media with multiple levels of recording layers and the recording method and apparatus therefor.
2. Description of the Related Art
With optical disks adapted for recording and reproduction, wobbled tracks are formed in the form of spirals and signals are recorded in track grooves or on lands between track grooves. Optical disks in which signals are recorded in grooves include CD-R disks, CD-RW disks, DVD-R disks, and DVD-RW disks. Optical disks adapted to record signals in grooves and on lands include DVD-RAM disks, in which signal recording is achieved by forming marks corresponding to signals on tracks using a laser beam.
Those recording media have wobbling tracks. Physical position signals on tracks are adapted to modulate a signal associated with wobbling (wobbling signal) as a carrier and the resulting modulated signals are recorded. Recording media of this type include CD-R disks, CD-RW disks, etc. In the DVD-RAM disks, the recording areas are formed in units of a predetermined recording capacity and physical address information is recorded in the form of embossed pits between each recording area. At the time of signal recording, each time the physical address information is detected, an information signal is recorded in the desired area.
The optical disk recording/reproducing system is divided into the CD system to adopt a laser beam of 780 nm in wavelength and the DVD system to adopt a laser beam of 650 nm. In recent years, working is proceeding with the next-generation of optical disks using a violet laser beam of 450 nm, which is intended to increase the recording density and recording capacity by making smaller marks with smaller beams.
As another technique to increase the recording capacity of recording/reproducing DVDs, the multi-layered structure is expected as used in DVD-ROM disks.
Recordable DVD types of optical disks include DVD-RAM disks, DVD-R disks, and DVD-RW disks, which are 12 cm in diameter and has a recording capacity of 4.7 gigabytes on each side. The DVD-ROM disks have each side double-layered as described above and have a capacity of 9 gigabytes on each side. Two-layered recording media have been implemented on the working level and are therefore expected to be mass-produced in the near future.
With such two-layered disks, in order to identify the layer which is being written on or read from, it is required to embed layer identification information in advance. For example, in the case of DVD, in a part of ID information for each sector is embedded layer number data as sector information. Reading the sector information allows the current layer to be identified.
However, the reading of the sector information needs a procedure of reading a block consisting of multiple sectors in sector synchronized state and then subjecting the block to error detection and correction. Only when the block is error free is the sector information identified.
Such a procedure is inconvenient in the event that recording has to be stopped quickly because of the occurrence of an interlayer jump during recording. This is due to the fact that the early layer identification is impossible with the above procedure.
In contrast, the occurrence of an intertrack or interlayer jump due to defects or vibrations during reproduction is not a serious problem. This is because, in the event that information subjected to error correction and then recovered as highly reliable data is determined through PID not to be target information, it is only required to discard that information and reperform the read operation. With reproduction, therefore, no problem arises except that the read time may be increased.
However, the occurrence of an interlayer jump during recording results in destruction of correct data already recorded, which becomes a serious problem. Destroying a large block of data, for example, a large quantity of data beyond the error correcting capability, by an interlayer jump resulting from malfunctions results in the inability to recover the data. That is, in the event of an interlayer jump, it is desirable to stop the recording operation as early as possible, i.e., before the error correcting capability is exceeded.
The aforementioned problem with respect to the interlayer jump also arises with an intertrack jump from one track to the adjacent one. It should be noted that the track pitch has progressively decreased with increasing recording density.
To perform tracking control using a read head, its object lens is controlled, but the mass of the object lens remains substantially the same as before. It has therefore become very difficult to prevent a jump to a separate track resulting from vibrations or defects, such as flaws, because the track spacing has become reduced.
On the occurrence of a track jump during recording, failure to record data on the correct track occurs, which can be solved by recording that data again. However, data already recorded are destroyed by new data and the recovery thereof becomes difficult.
As described above, in recording onto recording/reproducing media, it is required to achieve the detection of physical recording locations and the prevention of a jump to a separate track.
The detection of the recording initiation location can be achieved by multiple-detection of the constituents of the physical structure of optical disks. However, it is difficult to prevent the occurrence of a jump to a separate track resulting from defects or vibrations during recording. Consequently, it becomes important to minimize damage by detecting the jump and then stop the recording operation. In general, a track jump (including an interlayer jump) is accompanied by a tracking error signal large in magnitude, which, depending on the contents of defects, may not be detected. It is therefore important to, after the occurrence of a jump, detect recording being made on a track different from an intended track through the use of a separate signal. As apparatus for preventing wrong recording, a technique is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-213565; however, this is intended to prevent wrong recording between disks.
According to embodiments of the present invention to provide a recording medium, a signal recording method and apparatus, and a signal reproducing apparatus which, at the occurrence of a jump from a track in the process of being recorded to a separate track on a recording/reproducing media, permit the fact to be detected quickly through the use of physical marks, such as embossed pits, that form addresses of recording tracks on the media.
To achieve the above objects, a recording medium in which each recording track is divided into recording areas each of a predetermined recording capacity and, in each of the recording areas, its physical address is formed of embossed pits (or information containing the physical address is formed of marks, or the physical address is formed of marks, characterized in that embossed pit patterns (or the shape of the marks) are made different between adjacent tracks (or between adjacent layers).
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.